The invention relates to electrical feedthroughs for making electrical connections, particularly in a high temperature and pressure environment.
In oil and gas operations, it is often necessary to make an electrical connection from the outside to the inside of a housing which is either sealed, pressurized, or filled with fluid. Such electrical connections are used to transmit power and data signals. In subsea and downhole environments, these electrical connections are subjected to extreme temperatures and pressures, which can run as high as 500xc2x0 F. and 25,000 psi, respectively. For permanent installations in the subsea or downhole environment, it is important that these electrical connections are reliable. In particular, it is important that fluid is prevented from penetrating the electrical connections because the presence of fluid in the electrical connections can cause a short circuit in the system. It is also important that the electrical connections are able to insulate typical tool voltages after being sealed from conductive seawater and/or wellbore fluid.
In the oil and gas field, the term xe2x80x9celectrical feedthroughxe2x80x9d is used to refer to an electrical connector that operates with a certain pressure differential across it. In general, the electrical feedthrough includes one or more contact pins disposed within a connector body. The ends of the contact pins extend from the connector body for connection to circuit leads. The contact pins are sealed in an insulatirig body. The insulating body is typically made of glass or ceramic where moderate to high pressures and temperatures are concerned. Recently, the insulating body has also been made of a thermoplastic material such as polyetherketone (xe2x80x9cPEEKxe2x80x9d). The insulating body acts as a seal between the contact pins and the connector body. In downhole and subsea environments, the connector body is mounted in a seal bore in a pressure bulkhead. Typically, one or more elastomer seals are provided on the outer diameter of the connector body to form a seal between the connector body and the pressure bulkhead.
Under long-term exposure to high pressure and temperature and corrosive fluids, the elastomer seals will eventually fail, allowing fluid to enter the pressure bulkhead and reach the contact pins. If the invading fluid is conductive, which is usually the case in downhole and subsea environments, a short circuit may occur in the system, resulting in power and data loss. An alternative to using elastomer seals is to arrange the insulating body in a metal body that can be secured to the pressure bulkhead by a weld or metal-to-metal seal. This will prevent fluid from getting in between the pressure bulkhead and the metal body. This technique has been used in glass-sealed and ceramic-sealed electrical feedthroughs. However, the electrical connection may still be subject to failure. In the case of glass-sealed electrical feedthroughs, moisture can condense in the small glass interface between the contact pin and the metal body, leading to eventual short circuit in the system. In the case of ceramic-sealed feedthroughs, porosity of the ceramic material itself can lead to absorption of moisture and eventual short circuit.
In one aspect, the invention relates to an electrical feedthrough which comprises a connector body made of a metallic material, at least one contact pin inserted through a cavity in the connector body, and an insulating body made of a thermoplastic material formed between the connector body and the contact pin so as to provide a hermetic seal between the connector body and the contact pin.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.